Ex Parte Kwak et al

Board of Patent Appeals and Interferences

Dec 17, 2008

10673251 (B.P.A.I. Dec. 17, 2008)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte JOON-SEOP KWAK,
KYO-YEOL LEE,
JAE-HEE CHO,
and SU-HEE CHAE
____________

Appeal 2008-4747
Application 10/673,251
Technology Center 2800
____________

Decided: December 23, 2008
____________

Before CHARLES F. WARREN, CATHERINE Q. TIMM, and
MICHAEL P. COLAIANNI, Administrative Patent Judges.

TIMM, Administrative Patent Judge.

DECISION ON APPEAL
I. STATEMENT OF THE CASE
Appellants appeal under 35 U.S.C. § 134(a) from the Examiner’s
decision rejecting claims 1-4, 6, 9-27, and 31-35. We have jurisdiction
under 35 U.S.C. § 6(b). This case was heard on November 18, 2008.
Appeal 2008-4747
Application 10/673,251

We AFFIRM-IN-PART.
The invention relates to a method of fabricating semiconductor light-
emitting devices, particularly, GaN based Group III-V nitride semiconductor
light-emitting devices (Spec. ¶ [0002]). These devices include a number of
layers formed on a “high-resistant” substrate such as a sapphire substrate
(e.g., Spec. ¶ 17). Independent claims 1 and 23 require a step of dry etching
the high-resistant substrate (step (c)). The only other independent claim,
claim 12, does not require dry etching. Claim 12 is otherwise similar to
claim 1, except that instead of a light-shielding layer, step (d) of claim 12
requires the forming of a light-transmitting layer.
The Examiner rejects claims 1-4, 6, 9-27, and 31-35 under 35 U.S.C.
§ 103(a) as unpatentable over Kawai (US 6,468,902 B2 issued Oct. 22,
2002) in combination with Nunoue et al. (US 5,905,275 issued May 18,
1999).
In arguing against the rejection, Appellants group claims 1 and 23
(and claims dependent thereon) together as a single group, and argue claim
12 (and claims dependent thereon) separately as a second group (Br. 5-10).
In accordance with 37 C.F.R. § 41.37(c)(1)(vii), we select one claim to
represent each group. We select claims 1 and 12. 1
Claims 1 and 12 read as follows:
1. A method for fabricating a light-emitting device, the method
comprising:

1 Along with the Reply Brief of October 25, 2005, Appellant filed an
Amendment to claim 16. There is no indication that the Examiner entered
this Amendment (See Remand of Aug. 6, 2007, Notice of Non-compliant
Brief of Aug. 10, 2007, Ans. of Dec. 13, 2007). Because there is no
indication that the Amendment was entered, we do not consider the
arguments directed to amended claim 16 (Dec. 26, 2007 Reply Br. 2-3).
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(a) sequentially forming a first compound semiconductor layer,
an active layer, and a second compound semiconductor layer, which are for
inducing light emission, on a high-resistant substrate;

(b) forming a light-transmitting conductive layer on the second
compound semiconductor layer;

(c) dry etching a region of the high-resistant substrate using a
reaction gas comprising at least C12 or BC13 to expose the first compound
semiconductor layer; and

(d) forming a light-shielding conductive layer to cover the
exposed region of the first compound semiconductor layer.

12. A method for fabricating a light-emitting device, the method
comprising:

(a) sequentially forming a first compound semiconductor layer,
an active layer, and a second compound semiconductor layer, which are for
inducing light emission, on a high-resistant substrate;

(b) forming a light-reflecting conductive layer on the second
compound semiconductor layer;

(c) etching a region of the high-resistant substrate to expose the
first compound semiconductor layer; and

(d) forming a light-transmitting conductive layer to cover the
exposed region of the first compound semiconductor layer.

II. DISPOSITIVE ISSUES
The issues arising in this appeal are:
(A) with respect to claim 1, have Appellants shown a reversible error in
the Examiner’s finding of a suggestion to dry etch the sapphire substrate of
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Kawai as required by step (c) on the basis that Kawai teaches away from
such dry etching; and
(B) with respect to claim 12, have Appellants shown reversible error in
the Examiner’s finding that Nunoue suggests substituting a light-
transmitting conductive layer for non-light transmitting layers disclosed in
Kawai?

III. PRINCIPLES OF LAW
“The combination of familiar elements according to known methods
is likely to be obvious when it does no more than yield predictable results.”
KSR Int'l Co. v. Teleflex Inc., 127 S. Ct. 1727, 1739 (2007). However, when
the prior art teaches away from a combination, that combination is more
likely to be nonobvious. KSR, 127 S. Ct. at 1739–40. “A reference may be
said to teach away when a person of ordinary skill, upon reading the
reference, would be discouraged from following the path set out in the
reference, or would be led in a direction divergent from the path that was
taken by the applicant.” In re Gurley, 27 F.3d 551, 553 (Fed. Cir. 1994).
But the degree of “teaching away” depends on the particular facts. Id.
“Although a reference that teaches away is a significant factor to be
considered in determining unobviousness, the nature of the teaching is
highly relevant, and must be weighed in substance.” Id.

IV. FINDINGS OF FACT
The following enumerated findings of fact (“FF”) are of particular
relevance:
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Issue (A)
1. Kawai describes thinning and/or forming a via hole in the sapphire
substrate of a GaN FET light-emitting device (col. 3, ll. 27-35).
2. In discussing the prior art, Kawai states that it was known to form via
holes in GaAs substrates by wet etching using a sulfuric
acid/hydrogen peroxide solution or alkali solution. But, normally,
reactive ion etching (RIE) using a mixed gas of CCl2F2 and He or ion
milling was used (col. 2, ll. 8-20). However, according to Kawai, the
techniques used for thinning and forming via holes in GaAs FETs are
more difficult to employ in the sapphire substrates of GaN FETs (col.
2, ll. 26-29). Sapphire is much harder than GaAs (col. 2, ll. 29-31).
According to Kawai,
since sapphire is very stable in chemical property, wet
etching cannot be used without any effective etchant. As
to dry etching by RIE, since its etching rate is as very low
as several µm/hr in maximum, and there is no etching
mask having a selectivity acceptable for selective
etching. Therefore, it is actually impossible to make the
via hole with any of these methods.
(col. 2, ll. 37-44.)
3. Kawai suggests forming the via hole by first thinning the sapphire
substrate to a thickness of 100 µm or less “for example to a thickness
around decades of µm,” covering the bottom surface with an etching
mask 6 of stacked metal thin film, and wet etching with a solution of
phosphoric/sulfuric acid (col. 4, l. 65 to col. 5, l. 11). The etching rate
is approximately 10 µm/hr (col. 5, ll. 11-12).
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4. Nunoue describes a process of forming a GaN light-emitting device
using a sapphire substrate as a support and having n- and p-type
electrodes on both the top and bottom surfaces (col. 1, ll. 6-9).
5. Nunoue discloses that:

the etching rate of sapphire is very low in dry etching or
wet etching. For this reason, it is practically difficult to
form holes in a sapphire substrate usually having a
thickness of 350 µm or more without damaging gallium
nitride semiconductor layers.
(col. 1, ll. 61-65.)
6. Nunoue describes etching a 40 µm deep trench 11a in a 350 µm thick
sapphire substrate by using an amorphous carbon mask and dry
etching with a Cl2/Ar gas mixture (col. 4, ll. 47-49; Fig. 1a). Nunoue
also suggests forming a tapered contact hole 62 in a sapphire substrate
61 by “any appropriate method” although Nunoue does not exemplify
dry etching (col. 8, ll. 18-29; Fig. 7a).
7. Appellants, in their Specification, specify using dry etching using Cl2
or BCl3, but do not distinguish their dry etching process from those of
the prior art (Spec. ¶ [0084]).
Issue (B)
8. Kawai forms a metal film ((Ni or Cr)/Au and Au layers) on the
bottom surface of the sapphire substrate to make an electrical
connection with a metal layer above the via hole 8 and to radiate heat
(col. 5, ll. 28-38; see also col. 11, ll. 4-9 and ll. 37-39). Alternatively,
Kawai forms a n-side electrode by depositing a Ti/Al film (62) on the
bottom surface of the sapphire substrate (col. 13, ll. 45-47; Fig. 14).
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9. As shown in Figures 7A-G, in one embodiment Nunoue forms a
buried layer 65 to bury the via hole 62 before deposition of layers on
the other side of the substrate (col. 8, ll. 40-68). The buried layer 65
may be formed from ZnO, GaN, AlN, GaAlN, etc. (col. 8, ll. 52-56).
An n-type electrode 70 may be formed over the buried layer 65 on the
bottom side of sapphire substrate 61 when the buried layer is
conductive (col. 9, ll. 31-33). Nunoue does not disclose materials for
electrode 70 nor specify that the electrode or buried layer be light-
transmitting.

V. ANALYSIS
Issue (A)
Nunoue provides evidence that it was known in the art to dry etch
sapphire substrates with a Cl2/Ar gas mixture to obtain 40 µm deep trenches
in 350 µm thick substrates (FF 6). Both Kawai and Nunoue recognize that
the dry etching rate of sapphire is very low (FF 2, 5). Nunoue states it is
difficult to form via holes in 350 µm thick substrates, but Kawai teaches a
method of thinning the substrate to levels of below 100 µm before etching
(FF 2, 5). The evidence as a whole tends to show that those of ordinary skill
in the art understood that it was possible to etch thin substrates of sapphire to
form via holes.
Nunoue also discloses a useful mask for the etching procedure,
therefore, overcoming the problems noted by Kawai with respect to masking
(FF 2, 6).
While Kawai and Nunoue indicate that dry etching sapphire is slow,
there is no evidence that Appellants have overcome this problem themselves,
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particularly in substrates of the thickness specified by Kawai, i.e., less than
100 µm (FF 7).
Based on the weight of the evidence as a whole, we cannot agree with
Appellants that the degree of Kawai’s teaching away from dry etching with a
CCl2F2/He gas mixture (FF 2) is significant enough to overcome the prima
facie case of obviousness of dry etching with the Cl2/Ar gas mixture of
Nunoue (FF 6). One of ordinary skill in the art would have used the known
dry etching process for its predictable, albeit slow, result of etching of via
holes in the thinned substrates of Kawai. While Kawai teaches a different
wet etching process as useful, it is well settled that, in a § 103 inquiry, the
fact that a different embodiment is taught to be preferred is not controlling,
since all disclosures of the prior art must be considered. Merck & Co. v.
Biocraft Labs., Inc., 874 F.2d 804, 807 (Fed. Cir. 1989); In re Heck, 699
F.2d 1331, 1333 (Fed. Cir. 1983).
With respect to claim 1, Appellants have not shown a reversible error
in the Examiner’s finding of a suggestion to dry etch the sapphire substrate
of Kawai as required by step (c) on the basis that Kawai teaches away from
such dry etching.
Issue (B)
Turning to Issue (B), the issue arising for claim 12, we note that the
Examiner acknowledges that the metals Kawai deposits on the underside of
the sapphire substrate are non-light transmitting (Ans. 6). Kawai deposits
the metal layers to make an electrical connection, to radiate heat, or,
alternatively, to form an n-side electrode (FF 8). While Nunoue discloses
depositing a buried layer 65 on the underside of a sapphire substrate (FF 9),
the Examiner provides no reasonable basis for including such a buried layer
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in the structure of Kawai. The layer structure of Kawai is built in a different
sequence of steps (built before via hole etching) and it is not clear why one
of ordinary skill in the art would include a buried layer designed to fill the
via hole in preparation for depositing layers Kawai has already deposited.
Appellants have established that the Examiner reversibly erred in
finding that Nunoue suggests substituting a light-transmitting conductive
layer for non-light transmitting layers disclosed in Kawai.

VI. CONCLUSION
We sustain the rejection of claims 1-4, 6, 9-11, 23-27, and 31-35
under 35 U.S.C. § 103(a). We do not sustain the rejection of claims 12-22
under 35 U.S.C. § 103(a).

VII. DECISION
The decision of the Examiner is affirmed-in-part.

VIII. TIME PERIOD FOR RESPONSE
No time period for taking any subsequent action in connection with
this appeal maybe extended under 37 C.F.R. § 1.136(a)(1)(iv).
AFFIRMED-IN-PART

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